ParrotPalCalorie deficit calculator
A calorie deficit is eating a little less than your body uses. This calculator estimates your maintenance calories, then takes off 250 or 500 kcal a day. Enter your age, height and weight in kg or stones; nothing is sent anywhere.
Key facts
Maintenance calories are estimated here with the Mifflin-St Jeor equation, multiplied by a rough activity level. As a guide, the NHS says an average woman needs about 2,000 kcal a day and an average man about 2,500. A 500 kcal daily deficit is often quoted as about 0.5 kg a week, but that rule is rough and progress usually slows.
Your calorie deficit
EstimateA 500 kcal daily deficit is roughly 0.5 kg a week at first, by the rough 7,700 kcal-per-kg rule. Real progress is usually slower and bumpier.
This calculator needs JavaScript. The table below gives worked examples, and the method is explained under it.
How many calories should I eat to lose weight?
Start from your maintenance number, the calories that would keep your weight steady, and take off 250 to 500 kcal a day. A smaller deficit is easier to keep up and leaves more room for protein. Here are worked examples:
| Person | Maintenance | 500 kcal deficit |
|---|---|---|
| Woman, 45, 165 cm, 70 kg | 1,850 | 1,350 |
| Woman, 45, 165 cm, 85 kg | 2,060 | 1,560 |
| Woman, 45, 165 cm, 100 kg | 2,260 | 1,760 |
| Man, 45, 178 cm, 80 kg | 2,330 | 1,830 |
| Man, 45, 178 cm, 95 kg | 2,530 | 2,030 |
| Man, 45, 178 cm, 110 kg | 2,740 | 2,240 |
Mifflin-St Jeor resting estimate × 1.375 for light activity, rounded to the nearest 10 kcal. Estimates, not measurements.
How the calculator works
- Resting energy uses the Mifflin-St Jeor equation: 10 × weight (kg) + 6.25 × height (cm) − 5 × age, then +5 for men or −161 for women.
- Activity multiplies that by a rough factor: 1.2 mostly sitting, 1.375 lightly active, 1.55 moderately active, 1.725 very active. If in doubt, pick the lower one.
- The deficit takes 250 or 500 kcal off, rounded to the nearest 10.
Equations are estimates for groups of people, so yours can be off. The best test is your own weight trend over three or four weeks.
Why your deficit may be smaller than you think
Food diaries usually miss some calories: cooking oil, sauces, drinks and bites. In our members’ data, people logging about the same calories got very different results on the scale: see the 1,800-calorie paradox. Weekends add up too: the weekend effect.
Keep the muscle while you cut
A deficit takes fat and some lean mass. Enough protein and two short strength sessions a week help you keep more muscle. Work out your number with the protein calculator, and see what weights and cardio each burn.
Making weight for a jiu-jitsu competition? The divisions are on BJJ weight classes from JitsAI, our founder’s BJJ training app.
What the research says
The Mifflin-St Jeor equation was built from measured resting energy use in 498 healthy adults aged 19 to 78, normal weight and obese. It predicts groups well; any one person can sit above or below it.
Mifflin MD, St Jeor ST, Hill LA, et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition 51(2):241–7. doi:10.1093/ajcn/51.2.241
The energy in a kilo of weight change depends on body fat, so the familiar 7,700 kcal per kilo is only a rough rule.
Hall KD. (2008). What is the required energy deficit per unit weight loss?. International Journal of Obesity 32(3):573–6. doi:10.1038/sj.ijo.0803720
As a guide, the NHS says an average man needs about 2,500 kcal a day and an average woman about 2,000, varying with age, size and activity.
NHS (2026). Understanding calories. NHS website Healthy weight. www.nhs.uk
Research describes the people who were studied. Where we quote our own members’ figures, they are what members logged, and the method is on our methodology page.
Save your target in ParrotPal and log meals by voice or text. It keeps the running total for you. 4.7★ on the App Store · iPhone. Get it on the App Store
Questions people ask
How do I work out my calorie deficit?
Estimate your maintenance calories (this calculator uses the Mifflin-St Jeor equation and an activity factor), then eat 250 to 500 kcal a day less. Check your weight trend over three or four weeks and adjust.
Is a 500 calorie deficit good?
It’s a common starting point and is often quoted as about 0.5 kg a week, but that rule is rough and progress usually slows. If 500 leaves you with a very low number, choose a smaller deficit and talk to your GP or a dietitian.
How many calories should a woman eat to lose weight?
It depends on age, size and activity. As a guide, the NHS says an average woman needs about 2,000 kcal a day to maintain her weight, so many women lose weight on a little less. The calculator gives a personal estimate.
Can I use stones and pounds?
Yes. Choose “Stones and feet” and enter your weight in stones and pounds and your height in feet and inches.
Why am I not losing weight in a calorie deficit?
Usually because the deficit is smaller than it looks: logs miss oil, sauces, drinks and bites, and an equation can be off for any one person. Weigh a few meals, log everything for a fortnight and look at the trend, not one weigh-in.
Related guides and data
- All calorie guides
- Protein calculator
- Steps per day by age
- AI calorie trackers: how accurate are they?
- Data: the 1,800-calorie paradox
Please read. This page is general information, not medical or dietary advice. If you have a medical condition, are pregnant, or have a history of disordered eating, talk to your GP or a dietitian before changing how you eat. Figures are estimates.